The electronic structure of biologically important molecules containing the carbonyl C equals O group has been extrapolated via semi-empirical molecular orbital theory from the spectrum of simpler molecules. Thus the structure of the peptide chain is often modeled by simple amides and the structure of steroid hormones by acrolein. Recent evidence has indicated, however, that the spectrum of these simple molecules may have been misinterpreted. With modern computers, ab initio quantum chemistry calculations are now capable of predicting the excitation energy of the first few excited states of simple compounds to plus or minus 0.3eV. An extended Gaussian-orbital basis is used to find self-consistent-field wavefunctions for each state of interest. Then a separate configuration-interaction calculation with perturbation theory extrapolations is carried out for each state. Rydberg series limits can also be found from similar calculations on positive ions. In the proposed research these methods will be used to assign the spectrum of formamide, N-methyl acetamide and arolein. The theory of the electronic structure of the peptide linkage and of the enone group in steroid hormones will then be re-evaluated.